Actually, it's 6:30 for late seating. 8:30 for early seating. All messed up for veteran cruises since the norm is to have both shows AFTER dinner.
Good news is, for some shows they do a 3rd show at 10:30 pm. They did that for the Golden Mickeys. And even if you go to your assigned show, you have the option of seeing it a second time. The whole reason I have seating is so I don't have to rush in the evening. The early show for the late seating messed that all up.
But it is clear Disney does this for a reason. This was my 7th cruise, and the first where the ship was dead after 11 pm (except of course for New Years Eve). Disney is an early to bed, early to rise cruise, which may also explain why they don't pay US Customs to station an agent at the gangway in St. Thomas the entire time they are in port, instead of making everyone report at 6:30 am to customs on board.